Problem: $ { \left[\begin{array}{rr}{2} & {0} \\ {2} & {-1} \\ {-2} & {1}\end{array}\right]-\left[\begin{array}{rr}{3} & {4} \\ {0} & {1} \\ {2} & {1}\end{array}\right] = {?} } $
Answer: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}-{3} & {0}-{4} \\ {2}-{0} & {-1}-{1} \\ {-2}-{2} & {1}-{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-1} & {-4} \\ {2} & {-2} \\ {-4} & {0}\end{array}\right]}$